When President Barack Obama nominated the Christian geneticist Francis Collins to head the National Institutes of Health in 2009, some American scientists questioned whether someone who professed a strong belief in God was qualified to lead the largest biomedical research agency in the world.

This argument — that scientific inquiry is essentially incompatible with religious belief — has been gaining traction in some circles in recent years. In fact, according to a 2009 Pew Research Center survey, American scientists are about half as likely as the general public to believe in God or a higher, universal power. Still, the survey found that the percentage of scientists that believe in some form of a deity or power was higher than you may think — 51 percent.

Scientists throughout history have relied on data and observations to make sense of the world. But there are still some really big questions about the universe that science can’t easily explain: Where did matter come from? What is consciousness? And what makes us human?

Where did matter come from? What is consciousness? And what makes us human?

In the past, this quest for understanding has given scientists both past and present plenty of opportunities for experiencing wonder and awe. That’s because at their core, both science and religion require some kind of leap of faith — whether it’s belief in multiverses or belief in a personal God.

In chronological order, here’s a glimpse into what some of the world’s greatest scientists thought about the possibility of a higher power.

1Galileo Galilei (1564 – 1642)

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The astronomer and scientist Galileo Galilei was famously convicted of heresy by the Roman Catholic Church for supporting the theory that the planets revolved around the sun. In private letters, he confirmed that his beliefs hadn’t changed.

Writing to the Grand Duchess Christina of Tuscany, Galileo criticized philosophers of his time who blindly valued Biblical authority over scientific evidence.

“I do not feel obliged to believe that the same God who has endowed us with senses, reason and intellect has intended us to forego their use and by some other means to give us knowledge which we can attain by them. He would not require us to deny sense and reason in physical matters which are set before our eyes and minds by direct experience or necessary demonstrations.”

2Sir Francis Bacon (1561 – 1626)

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Known as the founder of the scientific method, Sir Francis Bacon believed that gathering and analyzing data in an organized way was essential to scientific progress. An Anglican, Bacon believed in the existence of God.

“God never wrought miracle to convince atheism, because his ordinary works convince it. It is true, that a little philosophy inclineth man’s mind to atheism; but depth in philosophy bringeth men’s minds about to religion. For while the mind of man looketh upon second causes scattered, it may sometimes rest in them, and go no further; but when it beholdeth the chain of them, confederate and linked together, it must needs fly to Providence and Deity.”

3Charles Darwin (1809 – 1882)

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Charles Darwin is best known for his theory of evolution. On the question of God, Darwin admitted in lettersto friends that his feelings often fluctuated. He had a hard time believing that an omnipotent God would have created a world filled with so much suffering. But at the same time, he wasn’t content to conclude that this “wonderful universe” was the result of “brute force.” If he pressed for a label, he wrote that the term “agnostic” would fit him best.

“I may say that the impossibility of conceiving that this grand and wondrous universe, with our conscious selves, arose through chance, seems to me the chief argument for the existence of God; but whether this is an argument of real value, I have never been able to decide. I am aware that if we admit a first cause, the mind still craves to know whence it came and how it arose. Nor can I overlook the difficulty from the immense amount of suffering through the world. I am, also, induced to defer to a certain extent to the judgment of the many able men who have fully believed in God; but here again I see how poor an argument this is. The safest conclusion seems to be that the whole subject is beyond the scope of man’s intellect; but man can do his duty.”

4Maria Mitchell (1818 – 1889)

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Maria Mitchell was America’s first female astronomer and the first woman to be named to the American Academy of Arts and Sciences. She was born into a Quaker family, but began to question her denomination’s teachings in her twenties. She was eventually disowned from membership and for the rest of her life, didn’t put much importance on church doctrines or attendance. Instead, she was a religious seeker who pursued a simpler sort of faith.

After hearing a minister preach about the dangers of science, Mitchell wrote:

“Scientific investigations, pushed on and on, will reveal new ways in which God works, and bring us deeper revelations of the wholly unknown.”

“The most beautiful thing we can experience is the Mysterious — the knowledge of the existence of something unfathomable to us, the manifestation of the most profound reason coupled with the most brilliant beauty. I cannot imagine a God who rewards and punishes the objects of his creation, or who has a will of the kind we experience in ourselves. I am satisfied with the mystery of life’s eternity and with the awareness of — and glimpse into — the marvelous construction of the existing world together with the steadfast determination to comprehend a portion, be it ever so tiny, of the reason that manifests itself in nature. This is the basics of cosmic religiosity, and it appears to me that the most important function of art and science is to awaken this feeling among the receptive and keep it alive.”

7Rosalind Franklin (1920 – 1958)

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Rosalind Franklin, who helped pioneer the use of X-ray diffraction, was born into a Jewish family in London. In letters to her father, Franklin made it clear that she seriously doubted the existence of an all powerful creator, or life after death.

When her father accused her of making science her religion, Franklin told him that she had a different definition of faith:

“In my view, all that is necessary for faith is the belief that by doing our best we shall come nearer to success and that success in our aims (the improvement of the lot of mankind, present and future) is worth attaining. Anyone able to believe in all that religion implies obviously must have such faith, but I maintain that faith in this world is perfectly possible without faith in another world…I see no reason to believe that a creator of protoplasm or primeval matter, if such there be, has any reason to be interested in our insignificant race in a tiny corner of the universe, and still less in us, as still more insignificant individuals.”

8Carl Sagan (1934 – 1996)

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Astronomer Carl Sagan is best known for hosting the TV series “Cosmos.” He rejected the label of “atheist” because he was open to the possibility that science would perhaps one day find compelling evidence to prove God. Nevertheless, he thought that the likelihood of that happening was very small. Instead, Sagan talked about “spirituality” as something that happens within the realm of material world, when humans encounter nature and are filled with awe.

“Science is not only compatible with spirituality; it is a profound source of spirituality. When we recognize our place in an immensity of light years and in the passage of ages, when we grasp the intricacy, beauty and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual.”

9Stephen Hawking (Born 1942)

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After years of hinting at it, physicist Stephen Hawking confirmed to the press in 2014 that he was an atheist. Hawkings doesn’t believe in a heaven or an afterlife and says that the miracles of religion “aren’t compatible” with science.

“Before we understood science, it was natural to believe that God created the universe, but now science offers a more convincing explanation.”

10Venkatraman Ramakrishnan (Born 1952)

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Venkatraman Ramakrishnan was born in an ancient town in Tamil Nadu, India, that is known for its famous temple dedicated to the Hindu deity Shiva. A physicist and molecular biologist, Ramakrishnan was awarded the 2009 Nobel Prize in chemistry for his research on ribosomes. While many Hindus consider astrology to be an important Vedic science and schedule life events around the movements of the stars, Ramakrishnan has spoken out against this practice in the past. He believes astrology evolved from humans’ desire to search for “patterns, generalize and believe.

“There is no scientific basis for how movement of planets and stars can influence our fate. There is no reason for time of birth to influence events years later. The predictions made are either obvious or shown to be random … A culture based on superstitions will do worse than one based on scientific knowledge and rational thoughts.”

11Neil deGrasse Tyson (Born 1958)

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Neil deGrasse Tyson is an astrophysicist and a popular television science expert. He told The Huffington Post thathe isn’t convinced by religious arguments about the existence of a “Judeo-Christian” god that is all-powerful and all-good, especially when he observes the death and suffering caused by natural disasters. Still, he told Big Think that while he’s often “claimed by atheists,” he’s actually more of an agnostic.

“I have found there is a wonderful harmony in the complementary truths of science and faith. The God of the Bible is also the God of the genome. God can be found in the cathedral or in the laboratory. By investigating God’s majestic and awesome creation, science can actually be a means of worship.”